Sometimes you have to protect interesting contents to get users' registration for commercial purposes or simply to create a community. But if content are not accessible, how can users know about their existance?
With this plugin the search engine can index these pages and bring to your site more visitors.
You can define an user for every search engine, and using the joomla 2.5/3.x ACL, you can define which pages are readable by each robots and by registered users and the pages which only registered users can read; or you can simply let spiders read all the pages.
Search engine robots are recognized and are automatically logged in, as a specific Joomla! user, so they are allowed to read the content reserved to that user or group.
This way contents are indexed, but no cache copy is made due the 'noarchive' meta tag, so an user can find the pages on the search engine, but he has to register to see the content of the page, because a normal visitor will not be logged in and he is redirect to the login/registration page!
PLEASE NOTE: IMPORTANT!
Without ip check, an advanced user can easily impersonate the bot of a search engine, so don't use this plugin to protect very confidential informations.
Of course confidential info should not be exposed on search engines, anyway! Ip check feature will be released in a future version.